2-vinyldibenzothiophene and method of preparing the same



Patented Feb. 28, 1950 .i {Z UNITED, STATES PATENT orrlce z-vmyLnmis uzo'rmornnna AND METHOD or PREPARING THE SAME Ralph G. Flowers and Leola W. Flowers, Pittsfield, Mass., assignors to General Electric Com pany, a corporation of New York No Drawing. Application .lune l'l, 1948, Serial No. 33,674

" Claims. (01. zeo se) The present invention relates to 2-vinyldibenzothiophene and methods for preparing the said compound.

We have discovered that monovinyldibenzothiophene, more particularly, 2-vinyldibenzothiophene which may be represented by the formula can be prepared by dehydrating an alpha-hydroxyethyldibenzothiophene, more particularly, 2- (alpha-hydroxyethyl) dibenzothiophene which may be represented by the formula Dibenzothiophene readily undergoes a Friedeb Crafts reaction with acetic anhydride and other acetylating agents in the presence of a Friedel- Crafts agent, e. g., aluminum chloride, aluminum bromide, ferric chloride, etc. The first product of the acetylization, as the reaction is generally carried out, is 2-acetyldibenzothiophene.

In addition, polyacetyldibenzothiophenes, for example, diacetyldibenzothiophenes, may be readily obtained by subjecting the monoketone isomer to further acetylization, if necessary, under more severe conditions. Thus, divinyldibenzothiophenes may be obtained from the diacetyldibenzothiophene'by employing the same method as that used for the monovinyldibenzothiophene as hereinafter described.

In order to facilitate control of the acetylization step, we have found it desirable to carryout the reaction in an inert solvent, i. e., a solvent 2 ma Friedel-Crafts reaction. Examples of such solvents are carbon disulfide, nitrobenzene, carbon tetrachloride, etc. In general, the catalyst is dissolved or suspended in the solvent and the mixture of dibenzothiophene and the acetylating agent is then added to the catalyst solution. If desired, the dibenzothiophene and the acetylating agent may be dissolved in a suitable solvent and the Friedel-Crafts catalyst is thereafter added to the solution.

The addition of the reactants to the catalyst solution must be carefully controlled in order that the temperature of the reaction mixture can b maintained in the range necessary for producing the desired ketone. The acetylization is preferably carried out at a temperature of from 30 C. to C. After completion of the reaction, the reaction mass is hydrolyzed and the organic layer is allowed to separate. The'following'equation illustrates the above-described reaction when acetic anhydride is employed as the acetylating agent and aluminum chloride the Friedel-Crafts catalyst:

The ketone may be separated from the other products comprising the organic layer as, for example, by distillation.

The next step in the preparation of the monovinyldibenzothiophenei is the reduction of the ketone to alpha hydroxyethyldibenzothiophene. This reduction may be carried out, for example, by hydrogenating the monoacetyldibenzothiophene in the presence of a hydrogenation catalyst, for example, finely divided platinum, platinum oxide, palladium, copper-chromium oxide,

reaction mixture.

pounds/sq. in., preferably at a pressure of about 1,500 pounds/sq. in. The reaction is carried out under such temperatures and for sufficient time to reduce all the ketone or ketones present in the The reduction of the ketone which, under the conditions of reaction, is inert to' the carbinol under the above-described con ditions may be illustrated by the following equation:

H Hydrogen (Ha) C-OH Catalyst -CHpt H ,s

The monovinyldibenzothiophene .is prepared. :1 from the alpha-hydroxyethyldibenzothiophene by dehydrating the latter. tion may be carried out by reacting ,the carbinol with any of the usual chemicalde'hydrating agents such as, for instance, potassium acid sul fate, zinc chloride, phosphoric anhydridew B60313.

However, We have found --.that in the production of. high boiling. polynucleanvinyl-compounds, such as-.-those.withtwhich our. invention. is concerned,

a direct/vapor phase-catalyticadehydrationis-theaprefer-red method. .This consists in dehydratingl;

theealphaehydroxyethyldibenzothiophene. in contact withactivatedalumina (A1203). alongor with other. s.metallic--=roxides,.-. for. :example; oxides of. chromium ,:.,tungsten,i molybdenum, manganese 6110.; more"particularly; by. passing the:-.carbinol-;

over the activated alumina or other rvapor. phase-.130.

dehydrationficatalystsl.inca systemwwhichz is main-- tained under; reduced -.,-pr.essure, for; example; -a pnessu-reof 0.1 mm. to :20 mm. mercury."

In carrying. out the dehydration,-..the. =cairzbinole i.

dissolved will. an inert. solvent: (ion example 2 111.35.

aromatic: hydrocarbon solvent, for instancepbenzenez toluene,-.etc-. is 'ted at a carefully controlledrate't to: a vertical. .reactioncolumn packedr. witlnt catalystipellets which maintained rat:v tempera-..

tunes appr eciably. .above the boiling: point. of. the. i140- caubinol r at.-th e.-.reducedi pressure" employed; for. 5 example, 325?;to. 450840;, more. particularly,.;340.

to 360 C. In other words, thecarbinol is vapor-x ized as it enters the reaction column and is maintained in the vapor phase in the" "presencemdouz of the catalyst fo'ras long as. it is necessary at .1 such temperatures so that polymerization of the monovinyldibenzothiophene, or an undesirable. condensation of the carbinol may not result. The

following-equationillustrates the vapor phase dehydration EI'BaOtiOIlIlIl which activated alumina is employed as the catalyst.

The crudeiproduct comprising-:the:monovinyldia: benzoth'iophen'e'may Toe-used as such, :but. prefer-x. ablysiisi purified by' suitable meansi-as;. fort. ex-u. ample} by recrystallization from a SUIUtiOHlLAICO -Ln hol":fiand sbnzene have :been'cfoundparticularly suitable as solventsifrfori carrying: routi this .".'re':-'-.-- crystallization;

order thatthose skill'edintheart may better2 understanda how the -present invention may. be practiced, "the followingizexamples are' giv'envby. way-pf:-illustration and: not by way oftlimitation;

p y EXAMBLEl 'Pitepurationirof. .2-aeetyldibenzothibphene 4-.

A miixture of. 20D.- grams dibenzothiophene and; 8illgrams acetyl chloride .Were dissolved in 1500120.

. lizationxofitth.mass-allowed to take place.

This dehydration Tea-C4 15.

equipped with a condenser, thermometer and stirrer. The temperature of the mixture was kept at about 35 C. while 400 grams of powdered aluminum chloride was slowly added. The temperature was then raised to 47 C. for 6 hours. The reaction mixture wasthereafter hydrolyzed byipouringnit into'a .mixture ofi ice and hydrochloric acid.' The product 'was then extracted vwith ether and the ether evaporated. The residue was mixed with methyl alcohol and crystal- The smail amount of crystals which separated out and were identified.-.as.- .2,8.-diacetyldibenzothiophene, 1\/LIP.."20'8'-20l?=C.,i.was removed by filtration and the.eresiduepfractionally distilled under vacuum to yielda large fraction boiling at about l98-204 "C5 at2 mm. Thismaterial recrystallized readily from-methyl alcohol to yield 2-acetyldibenzothiophene,M. P. ill-112 C.

EXAMPLE 2 Preparation .01 2Jmhihd hydroxyethylldibenzothiophen'e Am portion-z: of: the: 2- acetyldibenzothiophene (9718 grams) pne-pa'red' above n was dissolved in 1: l loflhco-xabsolute methyl? alcohol; and thereafter heated with shaking in a. hydrogenation bomb in the presence 1on5? grams of-copper-chromium oxide catalyst and hydrogen gas. Apressure of 1740 pounds of hydrogen-was introduced into the bomb at the start of the reaction. The temperature 'washeldvat 1363 Cjiors-ihours The' product. thusxzobtain'ediwasfiltere'daand recrystallized from alcohol as whitei ineedks having ca 'M Pslof showed the following .results Per Cent Per ECBDt Per Cent Carbon Hydrogen Sulfur EXAMPLEEB,

jPreparatiowoj z vinyldib'neoth'z'ophene 33 gnams of... 2- (alpha-hydrox-yethyl) dibenzo- 261.0-621) C. Analysis: rot; the .-2 latter product L thiophenedissolvedin 200 cc.'.benzene1were added dropwisei. intoa'a wertical: :column packed with aluminum oxide .pellets'. The. -.column was. held at..a temperature of:.= 32591-35090. during the .-re- 5 actionuand. the reactingavapors were drawn 7 through thecolumn-by ;a-vacuum= .pump which.

maintained a pressure of about: 10 mm. on the.

systems LTha-product. issuing from: the: tubev was recrystallized from :ethy1,;- alcohol assmall white needles,-.= .melting.-. ,at.-..45.0?+-45.5. C. which was identifiedas essentially. pure .2-vinyldibenzothiophene-as evidenced bywthe fo1lowing-.-ana1ytical The monomeric compound. 2-vinyldibenzothio-. phene may also be preparedas follows:

Eight 3 parts by weight, .Z-(aIpha-hydroxyeth'yl)t dibenzothiophne and 0.1 part of. the in! pstertiary .butyl catecholg. were heated ently in a porcelain crucible until they were melted. One part anhydrous copper sulfate was added to the mixture and the entire mass warmed gently for a few minutes. The 2-vinyldibenzothiophene thus formed was recrystallizedfrom alcohol in the same manner as employed in Example .3 above.

In general, the polymerization of the monovinyldibenzothiophene may be inhibited by the same compounds that inhibit the polymerization of styrene, for example, catechol, hydroquinone, etc. Such inhibitors may be washed out of the monomer with a dilute caustic solution if desired; or polymerization may be carried out in the pres ence of a small amount of inhibitor at an elevated temperature with or without a polymerization catalyst.

2-vinyldibenzothiophene is especially suitable for use in the preparation of polymers and copolymers that are useful in various industrial thiophene which comprises (1) forming a solution in an aromatic hydrocarbon solvent of 2- ,'(alpha-hydroxyethyl)dibenzothiophene and (2) passing the aforesaid solution over heated activated alumina at a temperature of from about I 325 to 450 C.

applications, for example, in the plastics and coating arts and as dielectric materials in the dielectric art. It may also be employed as starting materials in the preparation of other organic compounds. The homopolymer and copolymers of Z-vinyldibenzothiophene and methods of preparing the same are more particularly disclosed and claimed in our copending application Serial No. 33,675, filed concurrently herewith and assigned to the same assignee as the present invention.

What We claim as new and desire to secure by Letters Patent of the United States is:

1. z-vinyldibenzothiophene.

2. The method of preparing z-vinyldibenzothiophene which comprises dehydrating 2- (alpha-hydroxyethyl)dibenzothiophene by heating the latter thereby removing a hydrogen atom and a hydroxy group from adjacent carbon atoms of the alpha hydroxyethyl radical.

3. The method of preparing 2-vinyldibenzo- RALPH G. FLOWERS. LEOLA W. FLOWERS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,997,744 Putzer Apr. 16, 1935 FOREIGN PATENTS Number Country Date 426,476 Germany Mar. 1926 601,568 Great Britain May 7, 1947 OTHER REFERENCES Journal Organic Chem. 13, May, 1948, pp. 729 to 734.

Frank, Ind. and Eng. Chem, Mar., 1948, pp. 420-422. 

2. THE METHOD OF PREPARING 2-VINYLDIBENZOTHIOPHENE WHICH COMPRISES DEHYDRATING 2(ALPHA-HYDROXYETHYL) DIBENZOTHIOPHENE BY HEATING THE LATTER THEREBY REMOVING A HYDROGEN ATOM AND A HYDROXY GROUP FROM ADJACENT CARBON ATOMS OF THE ALPHA HYDROXYETHYL RADICAL. 